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International audience; In 2017-2019, a seismic swarm was triggered in the Maurienne valley (French Alps), with more than 5000 events detected by the regional SISmalp network. The population, who asked SISmalp to provide information on the processes and the associated risk, felt many earthquakes. In a post-L'Aquila trial context, we conducted a reflection on the scientific and social operational management of the crisis. The geological and tectonic analysis, the deployment of a temporary seismic network, an automatic double-difference relocation procedure (HypoDD) after clustering earthquakes, as well as the interactions with the population and the risk managers, have been carried out jointly. The length and unpredictability of the sequence complicated crisis management and the relations between local authorities and civil protection. The involvement of SISmalp, beyond its main scientific and observation prerogatives, has contributed to moderate the fears of the population by providing scientific explanations.

In moderate-to-low seismic hazard regions, estimating the socio-economic consequences of an earthquake on the urban scale is a costly and difficult task. This study analyses existing global earthquake databases to build a loss flat file of 445 earthquakes since 1967 with a magnitude greater than 4.5. The flat file includes information on the social consequences (fatalities, etc.) and economic losses (direct and indirect costs, number of buildings destroyed or damaged, etc.) of each earthquake. In this study, exposed population and GDP at the date of the earthquake complete the flat file information, estimated in relation to the ground motion footprint provided by USGS ShakeMap. TThe completeness of our catalog of social and economic losses is tested thanks to the creation of a synthetic database of losses of the 22 856 earthquakes between 1967 and 2015 affecting at least one country from the ISC-gem database. From these data, we propose a more realistic loss models. Then, occurrence models of human and direct economic losses relative to the exposed population and GDP per capita are derived showing that, although the number of casualties and the absolute magnitude of losses increase as a consequence of urban concentration, global losses relative to exposure decrease. Finally, the projection of future losses is discussed.

In moderate-to-low seismic hazard regions, estimating the socio-economic consequences of an earthquake on the regional scale is a costly and difficult task. This study analyses existing global earthquake databases to build a loss flat file of 445 earthquakes since 1967 with a magnitude greater than 4.5. The flat file includes information on the social consequences (e.g. fatalities and injuries) and economic losses (e.g. direct and indirect costs, number of buildings destroyed or damaged). In this study, exposed population and GDP at the date of the earthquake complete the flat file information, estimated thanks to the exposed area computed with an empirical relationship derived from the ground motion footprint provided by USGS ShakeMap. Earthquake consequences have increased since 1967 and follow a non-stationary Poisson distribution with rate proportional to exposure. In order to assess the stationarity of the consequences, we assumed stationary losses and fatalities by normalizing consequences by the exposed wealth and population verified on a sub-set of earthquakes for which exact population is given by national census. The completeness of the flat file catalogue is compared to the international seismological catalogue, and we compute the annual rate of exceedance of human and direct economic losses relative to the exposed population and the associated GDP per capita. We show that, although the number of casualties and the absolute magnitude of losses increase as consequence of urban concentration, global losses, relative to effective exposure corresponding to macroseismic intensity of at least V, decrease. (Access to the flat file: https://www.isterre.fr/philippe-gueguen/earthquake-losses-database/ ).